We wish to study the phosphorylation and dephosphorylation of various proteins of functionally different muscles in order to shed light on the molecular events of muscle contraction. Particular aspects of this long-range research aim are: Changes in the phosphate content of myosin light chains, tropomyosin, troponin-T, the 10,000 dalton acid chloroform-methanol soluble protein, and the proteins of the sarcoplasmic reticulum will be determined during a single isotonic or isometric tetanus of electrically stimulated frog muscle, electrical stimulation of the stretched muscle, and chemically induced contractures of the muscle. We plan to study the effect of denervation, neurotransmitters, and various drugs on the turnover of protein-bound phosphorus in skeletal muscle and the effect of inotropic agents on the phosphorylation of tropomyosin in perfused heart. We plan to compare the phosphorylation of tropomyosin in normal and hereditary dystrophic muscle. We plan to apply phosphorus nuclear magnetic resonance for the detection of phosphoryl tropomyosin and for the detection of changes in the environment of the tropomyosin-bound phosphate as a result of its interaction with the troponin complex and actomyosin. We plan to isolate the enzymes involved in the turnover of the tropomyosin-bound phosphate.